HIF-1a Expression and Implication in the Resistance Regulation and Malignancy in Pediatric Lymphomas Non-Hodgkin’s Tissue Arrays

The Non-Hodgkin lymphomas are one of the most common of pediatric tumor, represent a group of curable tumors whose therapeutically success depends mainly in an early diagnosis, a combined therapy and a correct stratification according to prognosis factors. Several molecules have been reported as prognosis factors in cancer. However, some patients become refractory to such treatments. Alternative treatment modalities include immunotherapy, though, even in the presence of an effective anti-tumor response, the tumor develops mechanisms of resistance to apoptotic stimuli and cross-resistance to immune-mediated cytotoxicity. The transcription factor HIF-1 a (Hypoxia-inducible factor-1a) has been associated to the expression of different genes related to cancer (e.g SDF-1 and VEGF) and is considered as a prognostic factor in several types of cancers such as: leukemia, oropharyngeal cancer, neck cancer and ovarian carcinoma among others. However until now there is no clear evidence that the expression of HIF-1a is involve in the pathogenesis of pediatric Non-Hodgkin lymphomas. Hence, we hypothesized that one mechanism of pediatric Non-Hodgkin lymphomas immune escape may be due to overexpression of HIF-1a and VEGF. This hypothesis was tested using Tissue Microarrays (TMA) of formalin fixed, paraffin embedded sections of 70 untreated pediatric patients with different Non-Hodgkin lymphomas, obtained from the Children’s Mexican Hospital, Federico Gomez (Mexico, City). Cases included since 2000 to 2006, tumors were classified as: Burkitt lymphoma (BL, 19 cases), large B cell lymphoma (LBCL, 6 cases), lymphoblastic lymphoma (LL, 13 cases), anaplastic large cell lymphoma (ALCL, 12 cases), Hodgkin lymphoma (HL, 10 cases), and other type of lymphomas (10 cases). Staining by immunohistochemistry was performed to determine the expression levels of HIF-1a. The immunostaining was scored and both the percent of positive cells and the intensity were recorded and the data were analyzed statistically. Preliminary analyses show a very high cytoplasm and nuclear overexpression of HIF-1a in tumor tissue compared with the control (non tumor tissue or reactive hyperplasia). Quantitative analysis of HIF-1a expression among the different tumor tissue show a significant statistical difference (p=0.0124, ANOVA), results of Tukey analysis for reactive hyperplasia (RH) and tumor tissue were: RH vs LL p = 0.0001, RH vs LBCL p = 0.0148, RH vs ALCL p < 0.04, RH vs BL p = 0.001, RH vs others p= 0.001. These studies suggest that overexpression of HIF-1 a may be involved in the pathogenesis of some pediatric Non-Hodgkin lymphomas (LL, LCGB, LCGA and BL) and is potential biomarker. Furthermore, inhibitors of HIF-1 a expression/activity may be targets for therapeutic intervention when combined with immunotherapy.